Have you ever found a solution to this problem? I am actually facing the same issue with Magento 2.3.1 and Porto.
I'm ALSO "in" for the answer to this miserable problem! PLEASE SOMEONE HELP!
After hours of research and debugging, I finally found that modifying the Cataclog Search settings from MySQL to Elasticsearch6+ fixed the problem on my website. NOTE: Your webhosting provider has to support this extension.
@dBox did you enable via the admin interface or via CLI? We've enabled ES6+ but still hit the error, pulling my hair out...
I changed from MySQL to elasticsearch6+ and then tested the connection, it shows could not be connected, from Magento admin panel. Please suggest.
Since I started the question I am able to answer the solution too.
The Porto theme is using extensions from Mageplaza and they need some updating.
What I did myself was disable the Magaplaza extensions, including the Mageplaza core extension. After that I installed the extensions from Mageplaza.
- Mageplaza Core
After installing them again I got the search to work again.
I don't use Composer to install extensions. I installed them manually in the app/code folder.
Chaning to Elastisearch won't work because you're provider needs to support this and has nothing to do why we get this error. It apparently has to do with the Mageplaza extensions which the Porto developers neglected to update. April 2019 was the last update on the theme and I'm waiting for a new update (hoping a lot of bugs are fixed).
If you have more questions please don't hesitate to ask ;-)
@Stevan1978did you find a soluton?
I have the same problem with porto theme using Mageplaza